Former U.S. Defense Secretary Donald Rumsfeld releases his memoir today, in which he admits "possible mistakes" but defends his handling of the wars in Afghanistan and Iraq.

In his book, "Known And Unknown," Rumsfeld acknowledges that the intelligence that Saddam Hussein had weapons of mass destruction -- one of the main justifications for launching the Iraq invasion in 2003 -- was wrong, but defends his decisions on the war.

In an interview with ABC news on the eve of the book's release, Rumsfeld said, "What you know today can help you unthink your thinking about tomorrow."

Rumsfeld said, "It can't help you with things you were thinking about back then," and added, "Back then there was reasonable confidence that [Saddam Hussein] had these weapons."

Rumsfeld, one of the most divisive members of his administration, served as defense secretary under former President George W. Bush from 2001 to 2006.